Towing to charge a Tesla

[Quicksilver]

I have read on here that a Tesla cannot be flat towed in case of running out of power or other breakdown.

But I'm watching YouTube today (my feed sends me a lot of Tesla related videos) and I see this video:


Would Tesla void the warranty if they knew you did this>

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[ldjessee]

The Tesla being towed charged is not broken down nor completely dead... and I think given all the things added to Tesla's to keep them from being abused for autopilot, I think the car would have to be on and a driver present to charge tow the car...

Because towed charging is just regenerative braking.

 

[android04]

I have read on here that a Tesla cannot be flat towed in case of running out of power or other breakdown.

But I'm watching YouTube today (my feed sends me a lot of Tesla related videos) and I see this video:


Would Tesla void the warranty if they knew you did this>

There's a difference between "cannot" and "is not approved by the manufacturer". You obviously can tow charge them as has been demonstrated multiple times. But Tesla does not approve of that for their own reasons. Maybe it's for liability reasons, or maybe it puts more stress on certain parts of the vehicle. But if they found out you did this and you have damage to your drive unit or battery pack or related systems, they could refuse to cover that specific damage under warranty.

 

[Crissa]

There's two basic reasons they don't approve of it: Not wanting to overload the motor/batteries - since the towing vehicle controls velocity and duration. The second is that usually when a vehicle needs towing, it may have damage. That damage might affect the systems in a way they can't control with software, and could result in extra flamey damage.

-Crissa

 

[HaulingAss]

There's two basic reasons they don't approve of it: Not wanting to overload the motor/batteries - since the towing vehicle controls velocity and duration. The second is that usually when a vehicle needs towing, it mau have damage. That damage might affect the systems in a way they can't control with software, and could result in extra flamey damage.

-Crissa

Because tow charging is just regen braking, the vehicle being towed would still be in charge of the duration of the charge and the specific amount of charge. Just as I drive down a steep mountain the vehicle may limit regen braking after a while, it would also limit regen if towed too far or too fast for whatever the battery temperature was.

Tesla probably doesn't endorse it simply because it's not that great of an idea. It's inefficient (wastes gas or diesel), it wears the tires of both the tow vehicle and the vehicle being towed at an accelerated rate, and towing is not one of the safest things you can do with two cars. Manufacturers regularly discourage certain actions for less tenuous reason than these.

All that said, I wouldn't hesitate to tow charge in a pinch (assuming my only problem was less charge than I needed to get to a convenient source of electricity). So, yeah, never tow charge a completely dead EV or one that has damage.

 

[Crissa]

Because tow charging is just regen braking, the vehicle being towed would still be in charge of the duration ...

No. The motors are always producing a charge when rotating.

The rest of what you said is right ^-^

-Crissa

 

[Quicksilver]

I watched the video of that guys wife in the Mercedes towing the Tesla with what was basically a tow strap that you use for snatching a stuck vehicle out.
There were so many things wrong with doing that.
Some other driver not seeing the strap and trying to move in between the tow car and towed vehicle. Her being inexperienced at towing another vehicle. Not a lot of common sense going on there.
I have had a lot of experience flat towing military vehicles with other military vehicles using a tow bar, safety chains and tow lights.
The CT with it's built in rear hitch would be ideal to pull another vehicle with a tow bar but said vehicle would have to have hard points to accept the feet of the tow bar on each side of the front end. There would also have to be a place to attach safety chains and tow lights. In the case of the CT magnetic tow lights are not going to stick to stainless steel. Yes you can just run the flashers but that makes changing lanes and braking a safety issue.
From what I saw the Tesla being towed/charged had one place where a plastic cover could be removed and a tow hook installed. There had to be a driver in the towed vehicle to steer it.
With a tow bar you hooked up and the rear vehicle would track behind the tow vehicle.
I could see this being done in an emergency but in my book you would be setting yourself up for a ticket (some states have strict regulations on towing) or having your insurance refuse to pay a claim if the towing caused an accident.

 

[Ogre]

Is there a safe way to do this for a long enough distance it will make a difference?

Towing with a towrope isn't really safe. Way too many failure modes. Also, seems like it would get even weirder when the second car isn't just dead weight, but is actively acting as a drag brake.

Going 70MPH for 25 miles on a 20-30 foot tether seems particularly unsafe to me. Margin of error if something goes wrong on the front car is quite small. Just look at how close behind the tow car is to the chase car.

If you're a Tesla owner and you get stranded.... don't listen to this irresponsible nonsense.

 

[tmeyer3]

there a safe way to do this for a long enough distance it will make a difference?

Yes, it can be done with a trailer and only 2 wheels contacting the road. It still works and is much safer. But as noted, this is a bad idea as regenerative braking is designed to assist in energy conservation. I say designed because I really don't think Tesla has tested or included software fail-safes for this kind of charging.

 

[HaulingAss]

No. The motors are always producing a charge when rotating.

The rest of what you said is right ^-^

-Crissa

Then what does Tesla do with the charge produced by the motors when I'm descending a long mountain grade and regen is reduced. I can feel the regen going away and the screen mentions regen has been reduced. I'm sure that Tesla can control the amount of charge sent to the battery otherwise the person who lives on top of a mountain and has charged their battery to 100% would be screwed. Their battery would be trashed.

This is how I know that towing a Tesla is not problematic from a battery management perspective.

 

[Crissa]

Then what does Tesla do with the charge produced by the motors when I'm descending a long mountain grade and regen is reduced.

The amount of regen can be reduced, but not eliminated, with some motors. Permanent magnet motors always produce some level of current when spun.

I did hear Porsche added resistor banks to the Taycan so that its regen is always consistent - they push the excess juice into the resistors if the battery is not ready for the energy.

-Crissa

 

[HaulingAss]

The amount of regen can be reduced, but not eliminated, with some motors. Permanent magnet motors always produce some level of charge when spun.

I did hear Porsche added resistor banks to the Taycan so that its regen is always consistent - they push the excess juice into the resistors if the battery is not ready for the energy.

-Crissa

So what do you think would happen to the car of a Tesla driver that lived on top of a mountain and charged to 100%

 

[Bill906]

Permanent magnet motors always produce some level of charge when spun.

Typical Surface mount PM motors will produce voltage when spun. On an industrial 3 phase inverter this can be a problem because there are diodes around the output transistors. If the PM motor is generating enough voltage it will flow back into the inverter. In the rare case where a PM motor of this type is used and significant regen is possible they would typically put a disconnect between the inverter and the motor.

I do not know PM SynRel motors well enough to know if they produce significant voltage when spun.

Induction motors will not produce voltage when spun by themselves. (Sometimes if there's residual magnatizm in the motor it could produce some voltage, but not enough to worry about.)

 

[Ogre]

So what do you think would happen to the car of a Tesla driver that lived on top of a mountain and charged to 100%

Well we know what happens to Mach E. My thought would be the car should apply old fashioned friction brakes if there is nowhere to push that EV power. Alternatively... crank up the climate control and cook the driver out since they were the chowderhead that put the car in this situation.

 

[Crissa]

So what do you think would happen to the car of a Tesla driver that lived on top of a mountain and charged to 100%

There's some headroom in the battery pack. I don't know what Tesla does, specifically.

I do believe it does increase the climate control in those situations, yes. Cool down the battery pack at maximum.

-Crissa

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